Retractor

ABSTRACT

A retractor for use in surgical operations comprises a pair of blade assemblies which are adapted to open about a set of axes that are not parallel to a third spatial axis. The retractor further comprises a pair of arms, which are adapted to move the pair of blade assemblies apart from one another in the third spatial axis. In operation, the blade assemblies are closed to assume a low profile, inserted into a relatively small incision, and stretched apart from each other, thereby stretching the skin about the incision to form an aperture longer than the incision. The blade assemblies are then opened by rotating the blades about the set of axes, thereby stretching the skin around the incision in a second direction that is substantially perpendicular to the first direction (i.e. the direction of the incision.) The retractor thus forms an aperture for passage of surgical instruments and viewing of the surgical field by surgical personnel. In some embodiments, the retractor features a pair of removable handles that may be removed from the arms during surgery in order to afford the surgeon improved space management about the incision. In specific embodiments, the invention provides a method of performing an operation, e.g. a spinal operation, on a patient using the disclosed retractor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority from U.S. Provisionalapplication Ser. No. 60/826,888, filed on Sep. 25, 2006, which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of surgery and moreparticularly to a retractor for use in inter alia surgery of the lowerback.

BACKGROUND OF THE INVENTION

Retractors are surgical devices used to spread bodily tissues in orderto allow a surgeon or surgical assistant to see and access a part of thebody that is to be surgically treated. In general, retractors comprise apair of jaws or blades that grip the bodily tissue and push it apartunder the force generated by an actuator, such as a pair of scissor-likearms having a distal end and a proximal end. The proximal end generallydefines a pair of handles and the distal end attaches to the pair ofblades so that manipulation of the handles causes the blades to moveapart from one another. Once an incision is made in the body to beoperated on, the blades are inserted into the incision and the actuatoris manipulated to move the blades of the retractor apart, thus spreadingthe tissue and providing an aperture through which the surgeon canaccess visualize the tissue to be surgically treated. One problem withthis type of retractor is that the aperture size is generally limited bythe size of the incision, meaning that a large aperture requires arelatively large incision. The drawback to this arrangement is thatlarger incisions result in the need for longer periods for healing ofthe incision. There is thus a need for a surgical retractor that iscapable of creating a relatively large aperture using a relatively smallincision, thereby reducing the invasiveness of the surgical procedure,post-operative healing times and patient discomfort.

SUMMARY OF THE INVENTION

The foregoing and other needs are met by embodiments of the presentinvention, which provide a retractor (surgical retractor) comprising:(a) a first blade assembly comprising a first blade rotatable about afirst axis, a second blade rotatable about said first axis and anadjuster in mechanical communication with the first and second bladesand adapted to rotate the first and second blades relative to each otherabout said first axis; (b) a second blade assembly comprising at least athird blade rotatable about a second axis and optionally a fourth bladerotatable about said second axis and, when said fourth blade is presentin said second blade assembly, an adjuster in mechanical communicationwith the third and fourth blades and adapted to rotate the third andfourth blades relative to each other about said second axis, whereinsaid second axis is different from said first axis; and (c) a means formoving said first blade assembly relative to said second blade assemblyalong a third axis that is not parallel to said first and second axes.

Further needs are met by embodiments of the present invention, whichprovide a method comprising the steps of: (a) providing a retractorcomprising: (i) a first blade assembly comprising a first bladerotatable about a first axis, a second blade rotatable about said firstaxis and an adjuster in mechanical communication with the first andsecond blades and adapted to rotate the first and second blades relativeto each other about said first axis; (ii) a second blade assemblycomprising at least a third blade rotatable about a second axis andoptionally a fourth blade rotatable about said second axis and, whensaid fourth blade is present in said second blade assembly, an adjusterin mechanical communication with the third and fourth blades and adaptedto rotate the third and fourth blades relative to each other about saidsecond axis, wherein said second axis is different from said first axis;and (ii) a means for moving said first blade assembly relative to saidsecond blade assembly along a third axis that is not parallel to saidfirst and second axes; (b) adjusting the first and second blades of thefirst blade assembly to be substantially parallel to each other to forma first closed blade assembly; (c) adjusting the third blade, and whenpresent the fourth blade, of the second blade assembly to besubstantially parallel to the first and second blades of the first bladeassembly; (d) making an incision in a tissue of a body; (e) insertingsaid first blade assembly and said second blade assembly within theincision; (f) moving the first blade assembly away from the second bladeassembly along said third axis and along the length of the incision sothat the incision is stretched to create an opening longer than theincision; and (g) adjusting the first and second blades of the firstblade assembly about said first axis to an open position, and, when saidfourth blade of said second blade assembly is present, adjusting thethird and fourth blades of the second blade assembly substantially aboutsaid second axis to an open position, thereby stretching the incisionout from said third axis and creating an aperture in the tissue that islonger and wider than the incision.

Other needs are met by embodiments of the invention, which provide aretractor comprising: (a) a first arm having a distal end and a proximalend; (b) a second arm having a distal end and a proximal end; (c) afirst blade assembly, attached near the distal end of the first arm andcomprising a first blade, a second blade and an adjuster in mechanicalcommunication with the first and second blades and adapted to rotate thefirst and second blades relative to each other about a first axis; (d) asecond blade assembly attached near the distal end of the second arm andcomprising at least a third blade rotatable about a second axis,optionally a fourth blade, and when the fourth blade is present, anadjuster in mechanical communication with the third and fourth bladesand adapted to rotate the third and fourth blades relative to each otherabout said second axis; and (e) an actuator adapted to move at least thedistal ends of said first and second arms relative to each other along athird axis that is not parallel to the first and second axes.

Further needs are met by embodiments of the present invention, whichprovide a method comprising the steps of: (a) providing a retractorcomprising: (i) a first arm having a distal end and a proximal end; (ii)a second arm having a distal end and a proximal end; (iii) a first bladeassembly, attached near the distal end of the first arm and comprising afirst blade, a second blade and an adjuster in mechanical communicationwith the first and second blades and adapted to rotate the first andsecond blades relative to each other about a first axis; (iv) a secondblade assembly attached near the distal end of the second arm andcomprising at least a third blade rotatable about a second axis,optionally a fourth blade, and when the fourth blade is present, anadjuster in mechanical communication with the third and fourth bladesand adapted to rotate the third and fourth blades relative to each otherabout said second axis; and (v) an actuator adapted to move at least thedistal ends of said first and second arms relative to each other along athird axis that is not parallel to the first and second axes; (b)ensuring that the first and second blades of the first blade assemblyare substantially parallel to each other to form a first closed bladeassembly; (c) ensuring that the third blade, and when present the fourthblade, of the second blade assembly are substantially parallel to thefirst and second blades of the first blade assembly; (d) making anincision in a tissue of a body; (e) inserting said first blade assemblyand said second blade assembly within the incision; (f) actuating theretractor such that said first blade assembly and second blade assemblyare moved apart from one another along the second axis and the incisionis stretched along the length of the incision to create an openinglonger than the incision; and (g) adjusting the first and second bladesof the first blade assembly along said first axis to an open position,and, when said fourth blade of said second blade assembly is present,adjusting the third and fourth blades of the second blade assemblysubstantially along said second axis to an open position, therebystretching the incision along the first axis and creating an aperture inthe tissue that is longer and wider than the incision.

Further needs are met by embodiments of the present invention, whichprovide a retractor comprising: (a) a first arm having a distal end anda proximal end; (b) a second arm having a distal end and a proximal end,at least said distal end of said second arm and said distal end of saidsecond arm being movable toward and away from each other; (c) a firstblade assembly attached near the distal end of the first arm, whichcomprises a first blade, a second blade and a means for moving saidfirst and second blades relative to each other about a first axis toadopt at least an opened position and a closed position; (d) a secondblade assembly attached near the distal end of the second arm, whichcomprises a third blade, a fourth blade and a means for moving saidthird and fourth blades relative to each other about a second axisdifferent from said first axis; and (e) a means for moving at least saiddistal end of said first arm and said distal end of said second armrelative to one another along a third axis that is not parallel to saidfirst and second axes.

Additional needs are met by embodiments of the present invention, whichprovide a method comprising the steps of: (a) providing a retractorcomprising: (i) a first arm having a distal end and a proximal end; (ii)a second arm having a distal end and a proximal end, at least saiddistal end of said second arm and said distal end of said second armbeing movable toward and away from each other; (iii) a first bladeassembly attached near the distal end of the first arm, which comprisesa first blade, a second blade and a means for moving said first andsecond blades relative to each other along a first axis to adopt atleast an opened position and a closed position; (iv) a second bladeassembly attached near the distal end of the second arm, which comprisesa third blade, a fourth blade and a means for moving said third andfourth blades relative to each other substantially along the first axisto adopt at least an opened position and a closed position; and (v) ameans for moving at least said distal end of said first arm and saiddistal end of said second arm relative to one another along a secondaxis; (b) ensuring that the first and second blades of the first bladeassembly are substantially parallel to each other; (c) ensuring that thethird and fourth blades of the second blade assembly are substantiallyparallel to each other and to the first and second blades of the firstblade assembly; (d) making an incision in a tissue of a body; (e)inserting said first blade assembly and said second blade assemblywithin the incision; (f) actuating the retractor such that said firstblade assembly and second blade assembly are moved apart from oneanother along the second axis and the incision is stretched along thelength of the incision to create an opening longer than the incision;and (g) adjusting the first and second blades of the first bladeassembly along said first axis to an open position, and, when saidfourth blade of said second blade assembly is present, adjusting thethird and fourth blades of the second blade assembly substantially alongsaid second axis to an open position, thereby stretching the incisionalong the first axis and creating an aperture in the tissue that islonger and wider than the incision.

The foregoing and additional needs are met by embodiments of theinvention described herein, which provide a retractor blade assembly,comprising: (a) a first blade having attached thereto a first barrel,the first barrel having a wall circling an axis and defining a firstlumen, a first channel in the wall having a first slope with respect tothe axis and a second channel in the wall having a second slope withrespect to the axis and having C2 symmetry about the axis with respectto the first slope, (b) a second blade having attached thereto a secondbarrel, the second barrel having a wall circling an axis and defining asecond lumen, a third channel in the second wall having a third slope ata third angle with respect to the axis, and a fourth channel in thesecond wall having a fourth slope at a fourth angle with respect to theaxis, the slope of the third angle being opposite in sign with respectto the axis to that of the first angle and the fourth channel having C2symmetry about the axis with respect to the third channel, wherein thefirst barrel fits within the second lumen of the second barrel such thatthe first and third channels intersect to form a first gap and thesecond an fourth channels intersect to form a second gap; (c) acylindrical plunger having an axis, an outer surface, a first end and asecond end, the first end having a hole through and at a right angle tothe plunger axis, and the second end having a screw thread cut into thesurface of the plunger, the cylindrical plunger fitting within the firstlumen of the first barrel such that said hole aligns with the first gapand the second gap and the hole, first gap and second gap forming apassage; (e) a rod fitting through the passage such that movement of theplunger along the axis causes the first barrel to rotate in a firstdirection and the second barrel to rotate in a second direction oppositethe first direction; (f) a holder possessing a third lumen, wherein thesecond barrel fits within the third lumen; and (g) a nut having aninternal screw thread and fitting over the end of the plunger; wherebyrotation of the nut causes the internal screw thread of the nut toengage the plunger screw thread and causes the plunger to move along itsaxis, thereby causing the first and second barrels to rotate about theaxis in opposite directions.

In some embodiments, both blade assemblies open so that when placedwithin the incision, both blades stretch the skin in a directionsubstantially perpendicular or oblique to the third axis. In someembodiments, the retractor has a lock, e.g. a ratchet lock, adapted tohold the retractor in an open position (i.e. the two arms spread apartfrom one another). In some embodiments, at least one blade iscomb-shaped, having two or more teeth adapted to engage the skin andpull it apart. In some such embodiments, the comb-shaped teeth areinterweaving so that they interlock when the blade assemblies areclosed. In other embodiments, at least one blade is fan shaped in thatit does not possess teeth. Such fan shaped blades may be substantiallyflat or may be bent or beveled in order to enhance the ability of theblades to lie flat when the blade assemblies are closed. In general,each blade assembly is hinged about an axis so that the blades open andclose like the covers on a book. This arrangement causes the bladeassembly to exert force on the skin about an incision in opposingdirections substantially perpendicular to the blade assembly axes andperpendicular or oblique to a cord defined by the points at which theblade assembly axes intersect the arms of the retractor. In someembodiments, the retractor includes a stabilizer, which maintains botharms parallel to one another. In particular embodiments, such astabilizer comprises a set of cross members between two substantiallyparallel arms, which move in such a way that as the arms open and close(i.e. move away from and toward one another, respectively), they areheld in an attitude that is substantially parallel to one another. Insome such embodiments, the actuator comprises a first handle connectedto the proximal end of the first arm and a second handle connected tothe proximal end of the second handle. This pair of handles may beremovable. Additionally, the pair of handles may include a biasingmember (e.g. a biasing spring) to hold the two handles apart. In someother embodiments, the arms are scissor-like arms, which cross oneanother and pivot about a pivot point. In such cases, although referenceis made to a third axis, which passes through the blade assemblies at anangle perpendicular or oblique to the blade assemblies, it is to beunderstood that the actual opening and closing of a scissor-like pair ofarms causes the ends of the arms to move in an arc. In some suchembodiments, each handle forms, along with its corresponding arm, andintegral unit. In other embodiments, the handles may be removable.Indeed, the blade assemblies, which fit at the ends of the arms, may beremovable as well. In some embodiments, the retractor may be provided toa surgeon or surgical personnel in the form of a kit comprisingadditional surgical articles and optionally instructions for the use andhandling of the retractor. Such additional surgical articles mayinclude: scalpels, suture needles, pedicle screws, suture material,spinal implant material, spinal fusion rods, biocompatible adhesive andclosure staples.

In some embodiments, the methods of the invention are surgical methodsthat include making an incision through a patient's skin. The methods ofusing the present invention are especially well suited for performingless invasive surgery, especially in the spinal region, and mostespecially in the lumbar region of the spine. In some embodiments, theincision is made in the lumbar region of the back near the spine; and insome particular embodiments, the method includes placing one or morepedicle screws in the spine. The pedicle screws are passed through theincision that is held open by the retractor of the invention, whichpermits the surgeon an excellent field of view of the area beingoperated on as well as ample space for passing the various surgicalarticles through the incision, while at the same time providing anincision which readily returns to its initial short length when theretractor is removed. Indeed one of the advantages of using theretractor of the present invention is that removal of the retractorafter the operation has been finished results in the incision tosubstantially the same shape and size as prior to retractor insertion.Thus, the retractor of the invention supports and makes possible lessinvasive surgery than heretofore was permitted with known retractors.

Such a retractor permits insertion of a relatively compact set ofretractor blades into a relatively short incision, opening of theincision in two non-parallel directions to make a surgical aperture thatis longer than the incision, and closing of the incision to present arelatively short incision for the surgical professional to close. Bystretching the tissue around the incision in two non-paralleldirections, the retractor of the invention allows the surgeon to make amuch smaller incision than is generally necessary using previously knownretractors. Thus, the retractor of the invention permits the surgicalprofessional to make less invasive incisions, while simultaneouslypermitting the professional to view and access the tissue that is to besurgically treated. Less invasive incisions generally provide shorterpatient recovery times, decreased patient discomfort and overallimproved outcomes as compared to the larger incisions necessitated bythe prior art retractors.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 provides a perspective view of a retractor of the invention witha pair of blade assemblies in a closed and parallel configuration.

FIG. 2 provides a perspective view of a retractor of the invention, thistime with the blades open in one direction along directional arrows cand d. Opening the retractor in this direction stretches the incisionalong its length.

FIG. 3 provides a perspective view of a retractor of the invention, nowwith the two blade assemblies open in separate directions from the firstdirection of opening. Opening the retractor blade assemblies stretchesthe incision open in a second direction that is different from, andessentially not parallel to, the first direction.

FIGS. 4, 5 and 6 provide exploded perspective views of a retractor ofthe invention, the handles being separated from the arm assembly and theblade assemblies being separated from the arm assembly.

FIGS. 7, 8 and 9 provide top views of the retractor of the invention.

FIGS. 10 and 11 provide close-up views of a blade assembly of theinvention.

FIG. 12 provides a perspective view of an arm assembly of the invention.

FIGS. 13-19 provide exploded views of a blade assembly of the invention,from which the assembly and operation of the blade assembly can bediscerned.

FIGS. 23-24 show side views of a first blade of a blade assembly, whileFIGS. 26-28 show side views of a second blade of a blade assembly.

FIGS. 20-22 show various blades that may be employed in blade assembliesof the invention.

FIGS. 29-30 show side views of barrels of blade assemblies according tothe invention. FIGS. 30 and 31 show the relationship between the anglesof slots in the first blade and the second blade of the blade assembly.

FIGS. 32-35 show perspective views of a retractor of the invention inoperation. A surgeon makes an incision having length L, into which theclosed blade assemblies of the retractor are inserted. The surgeon thenopens the retractor to create a lengthwise opening having length L′,wherein L′>L. Finally the surgeon opens the blade assemblies to create aL′×W′ aperture. In some embodiments, the handles 24, 44 can be removedfrom the arm assembly to permit the surgeon even greater ability to seeand operate on the tissue to be treated.

DETAILED DESCRIPTION OF THE INVENTION

The retractor of the invention provides advantages over the prior artretractors comprising a set of blades and an actuator, such as a set ofscissor arms. The retractor of the invention allows the person skilledin the art to insert a relatively compact set of retractor blades intoan incision having a short length. In some embodiments, the compact setof retractor blades are of such a size that they can be inserted withinthe incision so that they are snugly embraced by the side walls of theincision. Activation of an actuator causes the blades to move apart in adirection that is essentially parallel to the length of the incision.This causes the tissue to stretch in one direction, creating an openinghaving a length in that direction that is substantially longer than theincision. Once the retractor is opened in the first direction, theactuator may be locked open. Then a pair of adjusters on the bladeassemblies may be manipulated to open the blade assemblies, thus pullingthe incised tissue apart in directions that are not parallel to theincision. In some embodiments, these directions may be perpendicular,substantially perpendicular or oblique to the incision. Thus there isopened up an aperture that is substantially longer than the incision,and thus is substantially larger than would be possible using a priorart device. Thus in relative terms, the surgeon may use a smallerincision, and in some cases a much smaller incision, than would havebeen required with a prior art device. Moreover, removal of theretractor, e.g. by closing the blade assemblies, replacing the handles(if necessary), closing the arm assembly and removing the bladeassemblies from the incision, causes the incision to relax back to asize that is much smaller than would have resulted from use of the priorart retractor.

In some embodiments, the handles, the blade assemblies or both areremovable. In some embodiments, the blades of the blade assemblies maytake on a variety of shapes and sizes. In some embodiments, theinvention provides a kit comprising a plurality of retractors havingblades of various sizes, shapes or both. In some currently preferredembodiments, the invention provides a kit comprising one or more sets ofhandles, one or more arm assemblies and two or more blade assemblies(optionally of varying blade sizes and/or shapes). In some embodiments,the invention provides a kit comprising a retractor of the invention,optionally more than two blades, at least two of which differ from oneanother in size, shape or both, and one or more pedicle screws forperforming lumbar surgery. Thus, the invention provides a retractor ofthe invention, a variety of surgical kits for performing surgery,especially back surgery, and methods of using the retractor to performsurgery, and especially back surgery.

The foregoing and further needs are met by embodiments of the invention,which provide (a) a retractor comprising: (a) a first blade assemblycomprising a first blade rotatable about a first axis, a second bladerotatable about said first axis and an adjuster in mechanicalcommunication with the first and second blades and adapted to rotate thefirst and second blades relative to each other about said first axis;(b) a second blade assembly comprising at least a third blade rotatableabout a second axis and optionally a fourth blade rotatable about saidsecond axis and, when said fourth blade is present in said second bladeassembly, an adjuster in mechanical communication with the third andfourth blades and adapted to rotate the third and fourth blades relativeto each other about said second axis, wherein said second axis isdifferent from said first axis; and (c) a means for moving said firstblade assembly relative to said second blade assembly along a third axisthat is not parallel to said first and second axes. It is to beunderstood by one of ordinary skill in the art that, while at present apreferred embodiment of the invention uses a means for moving said firstblade assembly relative to said second blade assembly employs two armsthat are held parallel to one another by a means for stabilizing thearms, it is also possible for said means for moving said first bladeassembly relative to said second blade assembly to be a pair of crossingarms joined to one another at a pivot point. In such cases, the bladeassemblies move relative to one another along an arc. Nonetheless, theirgeneral direction of motion relative to one another, and the directionof motion that is of especial interest in the context of the presentinvention, is along an axis that is generally defined by a line passingthrough the blade assemblies, e.g. at the point where each bladeassembly is attached to its respective arm. In particular embodiments,the second blade assembly comprises a third blade, a fourth blade and anadjuster in mechanical communication with the third and fourth bladesand adapted to rotate the third and fourth blades relative to each otherabout said second axis. In some such embodiments, the first and secondaxes may be substantially coplanar with one another. Indeed in somecurrently preferred embodiments, the first and second axes are not onlycoplanar but also substantially parallel to one another. In particularembodiments, the first and second axes are coplanar with, parallel to,or at some pre-determined skew angle with respect to one another. Insome specific examples, the third axis is substantially perpendicular tothe first axis, the second axis or both the first and second axes. Inparticular embodiments, the third axis is substantially perpendicular toboth the first axis and the second axis. In some embodiments, the thirdaxis is perpendicular to the first axis, the second axis or both thefirst and second axes. In some specific embodiments, the third axis isperpendicular to both the first and second axes. In some embodiments,the retractor described herein possesses a means for locking said firstand second blade assemblies in at least one predetermined position alongsaid second axis. In some particular embodiments, two of said blades areof substantially different sizes in at least one dimension. In somespecific embodiments, at least two blades of different sizes form partof the same blade assembly, while in other embodiments, two blades ofdifferent sizes form parts of different blade assemblies. In someparticular embodiments, at least one of the first, second, third and,when present, forth blades is a comb-shaped blade. In some embodiments,at least one of the first, second, third and, when present, fourthblades is a substantially flat blade. In some embodiments, In someembodiments, the invention includes at least one removable bladeassembly. In some specific embodiments, both blade assemblies areremovable.

In some embodiments, the invention provides a method (e.g. a method ofsurgery—in particular spinal surgery, e.g. in the lumbar region of theback) comprising the steps of: (a) providing a retractor comprising: (i)a first blade assembly comprising a first blade rotatable about a firstaxis, a second blade rotatable about said first axis and an adjuster inmechanical communication with the first and second blades and adapted torotate the first and second blades relative to each other about saidfirst axis; (ii) a second blade assembly comprising at least a thirdblade rotatable about a second axis and optionally a fourth bladerotatable about said second axis and, when said fourth blade is presentin said second blade assembly, an adjuster in mechanical communicationwith the third and fourth blades and adapted to rotate the third andfourth blades relative to each other about said second axis, whereinsaid second axis is different from said first axis; and (iii) a meansfor moving said first blade assembly relative to said second bladeassembly along a third axis that is not parallel to said first andsecond axes; (b) adjusting the first and second blades of the firstblade assembly to be substantially parallel to each other to form afirst closed blade assembly; (c) adjusting the third blade, and whenpresent the fourth blade, of the second blade assembly to besubstantially parallel to the first and second blades of the first bladeassembly; (d) making an incision in a tissue of a body; (e) insertingsaid first blade assembly and said second blade assembly within theincision; (f) moving the first blade assembly away from the second bladeassembly along said third axis and along the length of the incision sothat the incision is stretched to create an opening longer than theincision; and (g) adjusting the first and second blades of the firstblade assembly about said first axis to an open position, and, when saidfourth blade of said second blade assembly is present, adjusting thethird and fourth blades of the second blade assembly substantially aboutsaid second axis to an open position, thereby stretching the incisionout from said third axis and creating an aperture in the tissue that islonger and wider than the incision. In some such embodiments, the secondblade assembly comprises a third blade, a fourth blade and an adjusterin mechanical communication with the third and fourth blades and adaptedto rotate the third and fourth blades relative to each other about saidsecond axis. In some particular embodiments, the first and second axesare substantially coplanar with one another, substantially parallel toone another and/or substantially perpendicular to the third axis. Thethird axis is the line passing through the points at which the bladeassemblies are joined to the arms of the retractor. As mentioned above,the person skilled in the art will recognize that when the arms arescissor-like arms that cross one another and are joined at a pivotpoint, the motion of the blade assemblies with respect to one anotherwill trace out an arc. However, the direction of motion of the two bladeassemblies with respect to one another will be essentially along thethird axis. In any case, in particular embodiments, the first and secondaxes are coplanar with one another, parallel to one another and/orperpendicular to the third axis. In particular embodiments, the thirdaxis is perpendicular to the first axis, the second axis or both thefirst and second axes. In some particular embodiments, the third axis isperpendicular to both the first and second axes. In some embodiments, atleast two of said blades are of substantially different sizes in atleast one dimension (e.g. length, width or both). In some specificembodiments, said two blades of different sizes form part of the sameblade assembly. In other specific embodiments, said two blades ofdifferent sizes form parts of different blade assemblies. In someembodiments, at least one of the first, second, third and, when present,fourth blades is a comb-shaped blade. In some embodiments, at least oneof the first, second, third and, when present, fourth blades is asubstantially flat blade. In some embodiments, the retractor furthercomprise a means for locking said first blade assembly and second bladeassembly in a position apart from each other along said second axis. Insome embodiments, the method further comprises removing at least a partof said means for moving the first and second blade assemblies towardand away from each other along the second axis. In some embodiments, theincision is made in the lumbar region of the back near the spine. Insome embodiments, the method further comprises placing one or morepedicle screws in the spine of the body. In other embodiments, themethod further comprises adjusting the first and second blade assembliesto closed positions and removing the retractor from the incision,thereby returning the incision to substantially the same shape and sizeas prior to retractor insertion. In still further embodiments, at leastone blade assembly is removable. In specific embodiments, both bladeassemblies are removable.

In some embodiments, the invention provides a kit for performing anoperation, comprising: (a) a retractor comprising: (i) a first bladeassembly comprising a first blade rotatable about a first axis, a secondblade rotatable about said first axis and an adjuster in mechanicalcommunication with the first and second blades and adapted to rotate thefirst and second blades relative to each other about said first axis;(ii) a second blade assembly comprising at least a third blade rotatableabout a second axis and optionally a fourth blade rotatable about saidsecond axis and, when said fourth blade is present in said second bladeassembly, an adjuster in mechanical communication with the third andfourth blades and adapted to rotate the third and fourth blades relativeto each other about said second axis, wherein said second axis isdifferent from said first axis; and (iii) a means for moving said firstblade assembly relative to said second blade assembly along a third axisthat is not parallel to said first and second axes; and (b) at least onemember of the group consisting of instructions for using the retractorto perform a surgical operation, scalpels, suture needles, pediclescrews, suture material, spinal implant material, spinal fusion rods,biocompatible adhesive and closure staples. In some embodiments, thesecond blade assembly of the retractor comprises a third blade, a fourthblade and an adjuster in mechanical communication with the third andfourth blades and adapted to rotate the third and fourth blades relativeto each other about said second axis. In some embodiments, the first andsecond axes are substantially coplanar with one another. In specificembodiments, the first and second axes are coplanar with one another. Insome embodiments, the third axis is substantially perpendicular to thefirst axis, the second axis or both the first and second axes. In someembodiments, the third axis is substantially perpendicular to both thefirst axis and the second axis. In some embodiments, the third axis isperpendicular to the first axis, the second axis or both the first andsecond axes. In some embodiments, the third axis is perpendicular toboth the first and second axes. In some embodiments, the retractorfurther comprises a means for locking said first and second bladeassemblies in at least one predetermined position along said secondaxis. In some embodiments, two of said blades are of substantiallydifferent sizes in at least one dimension. In particular embodiments,two blades of different sizes form part of the same blade assembly. Insome embodiments, two blades of different sizes form parts of differentblade assemblies. In some embodiments, at least one of the first,second, third and, when present, forth blades is a comb-shaped blade. Insome embodiments, at least one of the first, second, third and, whenpresent, fourth blades is a substantially flat blade. In someembodiments, at least one blade assembly is removable. In some specificembodiments, both blade assemblies are removable.

In some embodiments, the invention provides a retractor comprising: (a)a first arm having a distal end and a proximal end; (b) a second armhaving a distal end and a proximal end; (c) a first blade assembly,attached near the distal end of the first arm and comprising a firstblade, a second blade and an adjuster in mechanical communication withthe first and second blades and adapted to rotate the first and secondblades relative to each other about a first axis; (d) a second bladeassembly attached near the distal end of the second arm and comprisingat least a third blade rotatable about a second axis, optionally afourth blade, and when the fourth blade is present, an adjuster inmechanical communication with the third and fourth blades and adapted torotate the third and fourth blades relative to each other about saidsecond axis; and (e) an actuator adapted to move at least the distalends of said first and second arms relative to each other along a thirdaxis that is not parallel to the first and second axes. In someembodiments of the retractor, the second blade assembly comprises athird blade, a fourth blade and an adjuster in mechanical communicationwith the third and fourth blades and adapted to rotate the third andfourth blades relative to each other about said second axis. In someembodiments, the first and second axes are substantially coplanar withone another. In some embodiments, the first and second axes are coplanarwith one another. In some embodiments, the third axis is substantiallyperpendicular to the first axis, the second axis or both the first andsecond axes. In some embodiments, the third axis is substantiallyperpendicular to both the first axis and the second axis. In someembodiments, the third axis is perpendicular to the first axis, thesecond axis or both the first and second axes. In some embodiments, thethird axis is perpendicular to both the first and second axes. In someembodiments, the retractor further comprises a means for locking saidfirst and second blade assemblies in at least one predetermined positionalong said second axis. In some embodiments, at least two of said bladesare of substantially different sizes in at least one dimension (e.g.length, width or both). In some embodiments, two blades of differentsizes form part of the same blade assembly. In some embodiments, twoblades of different sizes form parts of different blade assemblies. Insome embodiments, at least one of the first, second, third and, whenpresent, forth blades is a comb-shaped blade. In some embodiments, atleast one of the first, second, third and, when present, fourth bladesis a substantially flat blade. In some embodiments, at least one bladeassembly is removable. In some embodiments, both blade assemblies areremovable. In some embodiments, the actuator comprises a stabilizerwhich maintains at least a portion of each of the first and second armsin an attitude substantially parallel to each other when the first andsecond arms are moved toward and away from each other. In someembodiments, the stabilizing member comprises a first crosspiece havingfirst and second ends, a second crosspiece having third and fourth ends,the first and second crosspieces being connected to each other by apivot, the first end of the first crosspiece being connected to thefirst arm by a pivot, the second end of the first crosspiece beingslidably connected to the second arm, the third end of the secondcrosspiece being connected to the second arm by a pivot and the fourthend of the second crosspiece being slidably connected to the first arm.In some specific embodiments, the first end of the first crosspiece isconnected to the first arm at a position distal to the slidableconnection of the fourth end of the second crosspiece to the first arm.In some more specific embodiments, the third end of the secondcrosspiece is connected to the second arm at a position distal to theslidable connection of the second end of the first crosspiece to thesecond arm. In some embodiments, the retractor further comprises a lockadapted to reversibly hold said first and second arms apart from eachother along the second axis. In some specific embodiments, the lock is aratchet lock comprising a ratchet blade and a ratchet release. In somemore specific embodiments, the ratchet lock holds the first arm and thesecond arm apart from each other along the second axis. In someembodiments, the actuator comprises a first handle connected to theproximal end of the first arm and a second handle connected to theproximal end of the second handle, wherein the first handle and thesecond handle are adapted to move the distal ends of the first andsecond arms toward and away from each other along the second axis. Insome specific embodiments, the first and second handles are connected bya pivot. In some additional embodiments, the actuator further comprisesa biasing member adapted to bias the actuator toward a preselectedcondition. In some specific embodiments, the biasing member is a biasingspring. In some embodiments, the biasing spring biases the distal endsof the first and second arms toward each other.

In some embodiments, the invention provides a method (e.g. a surgicalmethod for surgery on the spine, e.g. the lumbar region of the spine)comprising the steps of: (a) providing a retractor comprising: (i) afirst arm having a distal end and a proximal end; (ii) a second armhaving a distal end and a proximal end; (iii) a first blade assembly,attached near the distal end of the first arm and comprising a firstblade, a second blade and an adjuster in mechanical communication withthe first and second blades and adapted to rotate the first and secondblades relative to each other about a first axis; (iv) a second bladeassembly attached near the distal end of the second arm and comprisingat least a third blade rotatable about a second axis, optionally afourth blade, and when the fourth blade is present, an adjuster inmechanical communication with the third and fourth blades and adapted torotate the third and fourth blades relative to each other about saidsecond axis; and (v) an actuator adapted to move at least the distalends of said first and second arms relative to each other along a thirdaxis that is not parallel to the first and second axes; (b) ensuringthat the first and second blades of the first blade assembly aresubstantially parallel to each other to form a first closed bladeassembly; (c) ensuring that the third blade, and when present the fourthblade, of the second blade assembly are substantially parallel to thefirst and second blades of the first blade assembly; (d) making anincision in a tissue of a body; (e) inserting said first blade assemblyand said second blade assembly within the incision; (f) actuating theretractor such that said first blade assembly and second blade assemblyare moved apart from one another along the second axis and the incisionis stretched along the length of the incision to create an openinglonger than the incision; and (g) adjusting the first and second bladesof the first blade assembly along said first axis to an open position,and, when said fourth blade of said second blade assembly is present,adjusting the third and fourth blades of the second blade assemblysubstantially along said second axis to an open position, therebystretching the incision along the first axis and creating an aperture inthe tissue that is longer and wider than the incision. In someembodiments, the method optionally comprises adjusting the third andfourth blades of the second blade assembly to an open position. In someembodiments, the actuator comprises a means for locking the first andsecond arms in a position apart from each other along the second axis,wherein the method further comprises locking said first and second armsin a position apart from each other along the second axis. In someembodiments, the actuator further comprises a set of removable handles,the method optionally further comprising removing said set of removablehandles from the first and second arms. In other embodiments, theincision is made in the lumbar region of the back near the spine. Infurther embodiments, the method further comprises placing one or morepedicle screws in the spine of the body. In some embodiments the methodfurther comprises closing the first and second blade assemblies andremoving the retractor from the incision, thereby returning the incisionto substantially the same shape and size as prior to retractorinsertion.

In some embodiments, the invention provides a kit (e.g. a surgical kit,especially a spinal surgery kit, and most particularly a spinal surgerykit for surgery on the lumbar region of the spine. In some embodiments,the kit comprises: (a) a retractor comprising: (i) a first arm having adistal end and a proximal end; (ii) a second arm having a distal end anda proximal end; (iii) a first blade assembly, attached near the distalend of the first arm and comprising a first blade, a second blade and anadjuster in mechanical communication with the first and second bladesand adapted to rotate the first and second blades relative to each otherabout a first axis; (iv) a second blade assembly attached near thedistal end of the second arm and comprising at least a third bladerotatable about a second axis, optionally a fourth blade, and when thefourth blade is present, an adjuster in mechanical communication withthe third and fourth blades and adapted to rotate the third and fourthblades relative to each other about said second axis; and (v) anactuator adapted to move at least the distal ends of said first andsecond arms relative to each other along a third axis that is notparallel to the first and second axes; and (b) at least one member ofthe group consisting of instructions for using the retractor to performa surgical operation, scalpels, suture needles, pedicle screws, suturematerial, spinal implant material, spinal fusion rods, biocompatibleadhesive and closure staples. In some embodiments, the second bladeassembly comprises a third blade, a fourth blade and an adjuster inmechanical communication with the third and fourth blades and adapted torotate the third and fourth blades relative to each other about saidsecond axis. In some embodiments, the first and second axes aresubstantially coplanar with one another. In some embodiments, the firstand second axes are coplanar with one another. In some embodiments, thethird axis is substantially perpendicular to the first axis, the secondaxis or both the first and second axes. In some specific embodiments,the third axis is substantially perpendicular to both the first axis andthe second axis. In some embodiments, the third axis is perpendicular tothe first axis, the second axis or both the first and second axes. Insome embodiments, the third axis is perpendicular to both the first andsecond axes. In some embodiments, the retractor further comprises ameans for locking said first and second blade assemblies in at least onepredetermined position along said second axis. In some embodiments, twoof said blades are of substantially different sizes in at least onedimension. In some embodiments, at least two blades of different sizesform part of the same blade assembly. In some specific embodiments, twoblades of different sizes form parts of different blade assemblies. Insome other embodiments, at least one of the first, second, third and,when present, forth blades is a comb-shaped blade. In some embodiments,at least one of the first, second, third and, when present, fourthblades is a substantially flat blade. In some embodiments, at least oneblade assembly is removable. In some specific embodiments, both bladeassemblies are removable. In some embodiments, the actuator comprises astabilizer which maintains at least a portion of each of the first andsecond arms in an attitude substantially parallel to each other when thefirst and second arms are moved toward and away from each other. In somespecific embodiments, the stabilizing member comprises a firstcrosspiece having first and second ends, a second crosspiece havingthird and fourth ends, the first and second crosspieces being connectedto each other by a pivot, the first end of the first crosspiece beingconnected to the first arm by a pivot, the second end of the firstcrosspiece being slidably connected to the second arm, the third end ofthe second crosspiece being connected to the second arm by a pivot andthe fourth end of the second crosspiece being slidably connected to thefirst arm. In some embodiments, the first end of the first crosspiece isconnected to the first arm at a position distal to the slidableconnection of the fourth end of the second crosspiece to the first arm.In some embodiments, the third end of the second crosspiece is connectedto the second arm at a position distal to the slidable connection of thesecond end of the first crosspiece to the second arm. In someembodiments, the retractor further comprises a lock adapted toreversibly hold said first and second arms apart from each other alongthe second axis. In some specific embodiments, the lock is a ratchetlock comprising a ratchet blade and a ratchet release. In some morespecific embodiments, the ratchet lock holds the first arm and thesecond arm apart from each other along the second axis. In someembodiments, the actuator comprises a first handle connected to theproximal end of the first arm and a second handle connected to theproximal end of the second handle, wherein the first handle and thesecond handle are adapted to move the distal ends of the first andsecond arms toward and away from each other along the second axis. Insome embodiments, the first and second handles are connected by a pivot.In some embodiments, the actuator further comprises a biasing memberadapted to bias the actuator toward a preselected condition. In someembodiments, the biasing member is a biasing spring. in some specificembodiments, the biasing spring biases the distal ends of the first andsecond arms toward each other.

In some embodiments, the invention provides a retractor comprising: (a)a first arm having a distal end and a proximal end; (b) a second armhaving a distal end and a proximal end, at least said distal end of saidfirst arm and said distal end of said second arm being movable towardand away from each other; (c) a first blade assembly attached near thedistal end of the first arm, which comprises a first blade, a secondblade and a means for moving said first and second blades relative toeach other about a first axis to adopt at least an opened position and aclosed position; (d) a second blade assembly attached near the distalend of the second arm, which comprises a third blade, a fourth blade anda means for moving said third and fourth blades relative to each otherabout a second axis different from said first axis; and (e) a means formoving at least said distal end of said first arm and said distal end ofsaid second arm relative to one another along a third axis that is notparallel to said first and second axes. In some embodiments, the firstand second axes are substantially coplanar with one another. In somespecific embodiments, the first and second axes are coplanar with oneanother. In some embodiments, the third axis is substantiallyperpendicular to the first axis, the second axis or both the first andsecond axes. In some embodiments, the third axis is substantiallyperpendicular to both the first axis and the second axis. In someembodiments, the third axis is perpendicular to the first axis, thesecond axis or both the first and second axes. In some specificembodiments, the third axis is perpendicular to both the first andsecond axes. In some embodiments, the retractor further comprises ameans for locking said first and second blade assemblies in at least onepredetermined position along said second axis. In some embodiments, twoof said blades are of substantially different sizes in at least onedimension. In some embodiments, two blades of different sizes form partof the same blade assembly. In some embodiments, two blades of differentsizes form parts of different blade assemblies. In some embodiments, atleast one of the first, second, third and, when present, forth blades isa comb-shaped blade. In some embodiments, at least one of the first,second, third and, when present, fourth blades is a substantially flatblade. In some embodiments, at least one blade assembly is removable. Insome embodiments, both blade assemblies are removable. In someembodiments, the means for moving at least said distal end of said firstarm and said distal end of said second arm relative to one another alongthe second axis comprises a means for maintaining at least a portion ofeach of the first and second arms in an attitude substantially parallelto each other when the first and second arms are moved toward and awayfrom each other. In some embodiments, the retractor further comprises ameans for locking the first and second arms in at least one preselectedposition. In some embodiments, the means for moving at least said distalend of said first arm and said distal end of said second arm towardalong said third axis comprises a removable means for moving said firstarm and said second arm relative to each other along the second axis. Insome embodiments, the removable means for moving said first arm and saidsecond arm toward and away from each other further comprises a means forbiasing the arms toward or away from each other.

The invention further provides a method (e.g. a method of surgery, suchas spinal surgery, and in particular spinal surgery in the lumbar regionof the back) comprising the steps of: (a) providing a retractorcomprising: (i) a first arm having a distal end and a proximal end; (ii)a second arm having a distal end and a proximal end, at least saiddistal end of said second arm and said distal end of said second armbeing movable toward and away from each other; (iii) a first bladeassembly attached near the distal end of the first arm, which comprisesa first blade, a second blade and a means for moving said first andsecond blades relative to each other along a first axis to adopt atleast an opened position and a closed position; (iv) a second bladeassembly attached near the distal end of the second arm, which comprisesa third blade, a fourth blade and a means for moving said third andfourth blades relative to each other substantially along the first axisto adopt at least an opened position and a closed position; and (v) ameans for moving at least said distal end of said first arm and saiddistal end of said second arm relative to one another along a secondaxis; (b) ensuring that the first and second blades of the first bladeassembly are substantially parallel to each other; (c) ensuring that thethird and fourth blades of the second blade assembly are substantiallyparallel to each other and to the first and second blades of the firstblade assembly; (d) making an incision in a tissue of a body; (e)inserting said first blade assembly and said second blade assemblywithin the incision; (f) actuating the retractor such that said firstblade assembly and second blade assembly are moved apart from oneanother along the second axis and the incision is stretched along thelength of the incision to create an opening longer than the incision;and (g) adjusting the first and second blades of the first bladeassembly along said first axis to an open position, and, when saidfourth blade of said second blade assembly is present, adjusting thethird and fourth blades of the second blade assembly substantially alongsaid second axis to an open position, thereby stretching the incisionalong the first axis and creating an aperture in the tissue that islonger and wider than the incision. In some embodiments, the actuatorcomprises a means for locking the first and second arms in a positionapart from each other along the second axis, the method optionallyfurther comprising locking said first and second arms in a positionapart from each other. In some embodiments, the actuator furthercomprises a set of removable handles, optionally further comprisingremoving said set of removable handles from the first and second arms.In some embodiments, the incision is made in the lumbar region of theback near the spine. In some embodiments, the method further comprisesplacing one or more pedicle screws in the spine of the body. In someembodiments, the method further comprises closing the first and secondblade assemblies and removing the retractor from the incision, therebyreturning the incision to substantially the same shape and size as priorto retractor insertion.

The invention further provides a kit comprising: (a) a retractorcomprising: (i) a first arm having a distal end and a proximal end; (ii)a second arm having a distal end and a proximal end, at least saiddistal end of said first arm and said distal end of said second armbeing movable toward and away from each other; (iii) a first bladeassembly attached near the distal end of the first arm, which comprisesa first blade, a second blade and a means for moving said first andsecond blades relative to each other along a first axis to adopt atleast an opened position and a closed position; (iv) a second bladeassembly attached near the distal end of the second arm, which comprisesa third blade, a fourth blade and a means for moving said third andfourth blades relative to each other substantially along the first axisto adopt at least an opened position and a closed position; and (v) ameans for moving at least said distal end of said first arm and saiddistal end of said second arm relative to one another along a secondaxis; and (b) at least one member of the group consisting ofinstructions for using the retractor to perform a surgical operation,scalpels, suture needles, pedicle screws, suture material, spinalimplant material, spinal fusion rods, biocompatible adhesive and closurestaples. In some embodiments, the first and second axes aresubstantially coplanar with one another. In some embodiments, the firstand second axes are coplanar with one another. In some embodiments, thethird axis is substantially perpendicular to the first axis, the secondaxis or both the first and second axes. In some embodiments, the thirdaxis is substantially perpendicular to both the first axis and thesecond axis. In some embodiments, the third axis is perpendicular to thefirst axis, the second axis or both the first and second axes. In someembodiments, the third axis is perpendicular to both the first andsecond axes. In some embodiments, the retractor of the kit furthercomprises a means for locking said first and second blade assemblies inat least one predetermined position along said second axis. In someembodiments, at least two of said blades are of substantially differentsizes in at least one dimension. In some embodiments, at least twoblades of different sizes form part of the same blade assembly. In someembodiments, two blades of different sizes form parts of different bladeassemblies. In some embodiments, at least one of the first, second,third and, when present, forth blades is a comb-shaped blade. In someembodiments, at least one of the first, second, third and, when present,fourth blades is a substantially flat blade. In some embodiments, atleast one blade assembly is removable. In some embodiments, both bladeassemblies are removable. In some embodiments, the means for moving atleast said distal end of said first arm and said distal end of saidsecond arm relative to one another along the second axis comprises ameans for maintaining at least a portion of each of the first and secondarms in an attitude substantially parallel to each other when the firstand second arms are moved toward and away from each other. In someembodiments, the retractor of the kit further comprises a means forlocking the first and second arms in at least one preselected position.In some embodiments, the means for moving at least said distal end ofsaid first arm and said distal end of said second arm toward along saidthird axis comprises a removable means for moving said first arm andsaid second arm relative to each other along the second axis. In someembodiments, the removable means for moving said first arm and saidsecond arm toward and away from each other further comprises a means forbiasing the arms toward or away from each other.

The present invention further provides, in some embodiments, a retractorblade assembly, comprising: (a) a first blade having attached thereto afirst barrel, the first barrel having a wall circling an axis anddefining a first lumen, a first channel in the wall having a first slopewith respect to the axis and a second channel in the wall having asecond slope with respect to the axis and having C2 symmetry about theaxis with respect to the first slope, (b) a second blade having attachedthereto a second barrel, the second barrel having a wall circling anaxis and defining a second lumen, a third channel in the second wallhaving a third slope at a third angle with respect to the axis, and afourth channel in the second wall having a fourth slope at a fourthangle with respect to the axis, the slope of the third angle beingopposite in sign with respect to the axis to that of the first angle andthe fourth channel having C2 symmetry about the axis with respect to thethird channel, wherein the first barrel fits within the second lumen ofthe second barrel such that the first and third channels intersect toform a first gap and the second an fourth channels intersect to form asecond gap; (c) a cylindrical plunger having an axis, an outer surface,a first end and a second end, the first end having a hole through and ata right angle to the plunger axis, and the second end having a screwthread cut into the surface of the plunger, the cylindrical plungerfitting within the first lumen of the first barrel such that said holealigns with the first gap and the second gap and the hole, first gap andsecond gap forming a passage; (d) a rod fitting through the passage suchthat movement of the plunger along the axis causes the first barrel torotate in a first direction and the second barrel to rotate in a seconddirection opposite the first direction; (e) a holder possessing a thirdlumen, wherein the second barrel fits within the third lumen; and (f) anut having an internal screw thread and fitting over the end of theplunger; whereby rotation of the nut causes the internal screw thread ofthe nut to engage the plunger screw thread and causes the plunger tomove along its axis, thereby causing the first and second barrels torotate about the axis in opposite directions. In some embodiments of theblade assembly the third angle is opposite in sign and congruent withthe first angle and the fourth angle is opposite in sign and congruentwith the second angle. In some embodiments of the blade assembly atleast the first angle has a magnitude with respect to the axis of lessthan about 75°. In some embodiments of the blade assembly, each anglehas a magnitude with respect to the axis of less than about 75°. In someembodiments of the blade assembly each angle has a magnitude withrespect to the axis of about 20° to about 70°. In some embodiments ofthe blade assembly, each channel has a first end and a second end andthe nut and plunger are threaded so that the rod moves from the firstend of the channels to the second end within 1 to 10 full rotations ofthe nut. In some embodiments of the blade assembly, the rod moves fromthe first end to the second end of the channels within 2 to 8 fullrotations of the nut. In some embodiments of the blade assembly the rodmoves from the first end to the second end of the channels within 3 to 6full rotations of the nut. In some embodiments of the blade assembly,the rod moves from the first end to the second end of the channelswithin 4 to 6 full rotations of the nut. In some embodiments of theblade assembly, at least one blade is comb shaped. In some embodimentsof the blade assembly, both blades are comb shaped. In some embodimentsof the blade assembly, at least one blade is fan shaped. In someembodiments of the blade assembly, both blades are comb shaped. In someembodiments of the blade assembly, the holder is adapted to be removablyaffixed to an arm of a retractor. In some embodiments of the bladeassembly, the holder is irreversibly affixed to an arm of a retractor.

Thus, the invention provides a retractor as described herein, wherein atleast one blade assembly is a retractor blade assembly, comprising: (a)a first blade having attached thereto a first barrel, the first barrelhaving a wall circling an axis and defining a first lumen, a firstchannel in the wall having a first slope with respect to the axis and asecond channel in the wall having a second slope with respect to theaxis and having C2 symmetry about the axis with respect to the firstslope, (b) a second blade having attached thereto a second barrel, thesecond barrel having a wall circling an axis and defining a secondlumen, a third channel in the second wall having a third slope at athird angle with respect to the axis, and a fourth channel in the secondwall having a fourth slope at a fourth angle with respect to the axis,the slope of the third angle being opposite in sign with respect to theaxis to that of the first angle and the fourth channel having C2symmetry about the axis with respect to the third channel, wherein thefirst barrel fits within the second lumen of the second barrel such thatthe first and third channels intersect to form a first gap and thesecond an fourth channels intersect to form a second gap; (c) acylindrical plunger having an axis, an outer surface, a first end and asecond end, the first end having a hole through and at a right angle tothe plunger axis, and the second end having a screw thread cut into thesurface of the plunger, the cylindrical plunger fitting within the firstlumen of the first barrel such that said hole aligns with the first gapand the second gap and the hole, first gap and second gap forming apassage; (d) a rod fitting through the passage such that movement of theplunger along the axis causes the first barrel to rotate in a firstdirection and the second barrel to rotate in a second direction oppositethe first direction; (e) a holder possessing a third lumen, wherein thesecond barrel fits within the third lumen; and (f) a nut having aninternal screw thread and fitting over the end of the plunger; wherebyrotation of the nut causes the internal screw thread of the nut toengage the plunger screw thread and causes the plunger to move along itsaxis, thereby causing the first and second barrels to rotate about theaxis in opposite directions. In some embodiments, the third angle isopposite in sign and congruent with the first angle and the fourth angleis opposite in sign and congruent with the second angle. In someembodiments, at least the first angle has a magnitude with respect tothe axis of less than about 75°. In some embodiments, each angle has amagnitude with respect to the axis of less than about 75°. In someembodiments, each angle has a magnitude with respect to the axis ofabout 20° to about 70°. In some embodiments, each channel has a firstend and a second end and the nut and plunger are threaded so that therod moves from the first end of the channels to the second end within 1to 10 full rotations of the nut. In some embodiments, the rod moves fromthe first end to the second end of the channels within 2 to 8 fullrotations of the nut. In some embodiments, the rod moves from the firstend to the second end of the channels within 3 to 6 full rotations ofthe nut. In some embodiments, the rod moves from the first end to thesecond end of the channels within 4 to 6 full rotations of the nut. Insome embodiments, at least one blade is comb shaped. In someembodiments, both blades are comb shaped. In some embodiments, at leastone blade is fan shaped. In some embodiments, both blades are combshaped. In some embodiments, the holder is adapted to be removablyaffixed to an arm of a retractor. In some embodiments the holder isirreversibly affixed to an arm of a retractor.

In some embodiments, the invention provides a kit comprising a retractoras described herein, wherein at least one blade assembly comprises: (a)a first blade having attached thereto a first barrel, the first barrelhaving a wall circling an axis and defining a first lumen, a firstchannel in the wall having a first slope with respect to the axis and asecond channel in the wall having a second slope with respect to theaxis and having C2 symmetry about the axis with respect to the firstslope; (b) a second blade having attached thereto a second barrel, thesecond barrel having a wall circling an axis and defining a secondlumen, a third channel in the second wall having a third slope at athird angle with respect to the axis, and a fourth channel in the secondwall having a fourth slope at a fourth angle with respect to the axis,the slope of the third angle being opposite in sign with respect to theaxis to that of the first angle and the fourth channel having C2symmetry about the axis with respect to the third channel, wherein thefirst barrel fits within the second lumen of the second barrel such thatthe first and third channels intersect to form a first gap and thesecond an fourth channels intersect to form a second gap; (c) acylindrical plunger having an axis, an outer surface, a first end and asecond end, the first end having a hole through and at a right angle tothe plunger axis, and the second end having a screw thread cut into thesurface of the plunger, the cylindrical plunger fitting within the firstlumen of the first barrel such that said hole aligns with the first gapand the second gap and the hole, first gap and second gap forming apassage; (d) a rod fitting through the passage such that movement of theplunger along the axis causes the first barrel to rotate in a firstdirection and the second barrel to rotate in a second direction oppositethe first direction; (e) a holder possessing a third lumen, wherein thesecond barrel fits within the third lumen; and (f) a nut having aninternal screw thread and fitting over the end of the plunger; wherebyrotation of the nut causes the internal screw thread of the nut toengage the plunger screw thread and causes the plunger to move along itsaxis, thereby causing the first and second barrels to rotate about theaxis in opposite directions.

In some embodiments, the invention provides a method as described hereinusing a retractor as described herein, wherein at least one bladeassembly is a retractor blade assembly, comprising: (a) a first bladehaving attached thereto a first barrel, the first barrel having a wallcircling an axis and defining a first lumen, a first channel in the wallhaving a first slope with respect to the axis and a second channel inthe wall having a second slope with respect to the axis and having C2symmetry about the axis with respect to the first slope; (b) a secondblade having attached thereto a second barrel, the second barrel havinga wall circling an axis and defining a second lumen, a third channel inthe second wall having a third slope at a third angle with respect tothe axis, and a fourth channel in the second wall having a fourth slopeat a fourth angle with respect to the axis, the slope of the third anglebeing opposite in sign with respect to the axis to that of the firstangle and the fourth channel having C2 symmetry about the axis withrespect to the third channel, wherein the first barrel fits within thesecond lumen of the second barrel such that the first and third channelsintersect to form a first gap and the second an fourth channelsintersect to form a second gap; (c) a cylindrical plunger having anaxis, an outer surface, a first end and a second end, the first endhaving a hole through and at a right angle to the plunger axis, and thesecond end having a screw thread cut into the surface of the plunger,the cylindrical plunger fitting within the first lumen of the firstbarrel such that said hole aligns with the first gap and the second gapand the hole, first gap and second gap forming a passage; (d) a rodfitting through the passage such that movement of the plunger along theaxis causes the first barrel to rotate in a first direction and thesecond barrel to rotate in a second direction opposite the firstdirection; (e) a holder possessing a third lumen, wherein the secondbarrel fits within the third lumen; and (f) a nut having an internalscrew thread and fitting over the end of the plunger; whereby rotationof the nut causes the internal screw thread of the nut to engage theplunger screw thread and causes the plunger to move along its axis,thereby causing the first and second barrels to rotate about the axis inopposite directions.

The invention will now be further described with reference to theappended drawings. In FIG. 1 there is shown a perspective view of aretractor 10 according to the present invention. The retractor 10comprises a first arm 12, having a distal end 14 to which is attached afirst blade assembly 16, comprising a first blade 18, a second blade 20and an adjuster 22; a second arm 32, having a distal end 34, to which isattached a second blade assembly 36 comprising a third blade 38, afourth blade 40 and an adjuster 42. The retractor further comprises afirst handle 24 having a distal end 28 and a proximal end 26 and asecond handle 44 comprising a distal end 48 and a proximal end 46. Thetwo handles 24 and 44 are joined to one another by a pivot 50 and arespanned by a biasing spring 52. The retractor 10 further comprises aratchet lock 54, which has serrations 56 that are adapted to engage anengagement member 58, which together with the ratchet lock 54 serves tohold the retractor in a particular position. In FIG. 1, the retractor 10is shown in the “closed” position, meaning that the two blade assemblies16 and 36 are relatively close to one another, as are the two arms 12and 32 and the distal ends 28 and 48 of the handles 24 and 44,respectively. Depression of the proximal ends 26 and 46 of handles 24and 44, respectively, in the directions of the arrows a and b results inthe blade assemblies 16 and 36 moving apart along the directional arrowsc and d, thus causing retractor 10 to assume the configuration depictedin FIG. 2. Note that the directional arrows c and d define a geometricline passing through and joining axis f, which passes vertically throughfirst adjuster 22, and axis g, which passes vertically through secondadjuster 42. Hereinafter axis f may be referred to alternatively as afirst axis, axis g may be referred to alternatively as a second axis andthe axis defined by directional arrows c and d may alternatively bereferred to as a third axis. The importance of these axes will becomeevident upon consideration of the remaining figures.

As can be seen in FIG. 2, the retractor 10 is in an “open” position,meaning that the first blade assembly 16 is relatively separated fromthe second blade assembly 36 along the third axis defined by directionalarrows c and d. Thus, as the blade assembly 16 moves along line d andblade assembly 36 moves along line c they exert force in the directionof lines d and c, respectively. Insertion of the blade assemblies 16 and36 into an incision (not shown) in a closed position (as in FIG. 1) andopening the blade assemblies 16 and 36 to an open position (as in FIG.2) results in a stretching of the incision along the same axis definedby directional lines c and d.

It is noted that in the embodiment depicted in FIGS. 1 and 2, theactuator comprises a pair of arms 12 and 32 and a pair of handles 24 and44. The person skilled in the art will recognize that other embodimentsof an actuator may be used. For example, scissor-like actuators areknown in the clamp and retractor arts. In some such embodiments, theactuator comprises a pair of handles such as those depicted in FIG. 1having attached at the distal ends of the handles 28 and 48 a pair ofblade assemblies 16 and 36 according to the invention. Moreover, whilethe handles 24 and 44 are depicted as being roughly parallel and joinedtogether at a pivot point 50, it is also within the skill in the art touse a pair of crossed (e.g. scissor-like) handles joined by a pivot.These and other embodiments of actuators are known in the art andcontemplated as being within the scope of some aspects of the invention.It is also to be understood that when the actuator is a scissor-likeembodiment, the motion of blade assemblies 16 and 36 traverse an arcrather than a straight line upon opening of the retractor. Nevertheless,the spatial relationship of the two blade assemblies 16 and 36 can beconceptualized as changing along a line described by arrows c and d,which for the purpose of brevity is referred to herein as an axis, andin particular the third axis (axes f and g being the first and secondaxes).

Turning adjuster 22 about axis f in the direction of adjustment arrow h,and adjuster 42 about axis g in the direction of adjustment arrow j,results in opening of the blade assemblies 16 and 36, respectively, asdepicted in FIG. 3. As shown in FIG. 3, opening of the blade assembly 16causes the blade 20 to exert force in the direction of direction arrown, while blade 18 exerts force in the direction of direction arrow p.Likewise, opening of blade assembly 36 causes blade 40 to exert force inthe direction of arrow k, while blade 38 exerts force in the directionof arrow m. Thus, after insertion of the closed blade assemblies 16 and36 of a closed retractor 10 in an incision, opening the retractor 10 andthen opening the blade assemblies 16 and 36, the retractor 10 createsand maintains an aperture in the incised tissue that is both longer(i.e. dimensionally larger in the direction of the incision) and wider(i.e. dimensionally larger in a direction perpendicular or oblique tothe direction of the incision) than the incision. It is to be understoodthat, while this description is especially apt where the incision is astraight line incision of about 0.1 to about 3 inches in length, it canapply to any shape of incision (e.g. an arc, a sinusoid, etc.) of anylength. In particular embodiments of the invention, the contemplatedsize of the incision is about 0.5 to 2 inches in length and the bladeassemblies 16 and 36 are appropriately sized so that when the retractor10 is closed the blade assemblies 16 and 36 fit lengthwise within theincision without requiring substantial stretching of the incised tissueprior to opening of the retractor 10. Thus, in some embodiments, theblades 18, 20, 38 and 40 are sized to snugly fit within the incisionwhen the blade assemblies are closed and the retractor is in a closedposition.

FIG. 4 shows the device 10 with handle assembly 2, comprising inter aliathe handles 24 and 44, separated from arm assembly 4, comprising interalia arms 12 and 32. As can be seen in FIG. 4, the distal end 28 ofhandle 24 has a connecting pin 62 that fits within a connecting hole 64on the first arm 12, while the distal end 48 of handle 44 has aconnecting pin 82 that fits within a connecting hole 84 in the arm 32.In the depicted embodiment, the blade assembly 16 is removable from thedistal end 14 of arm 12 and the blade assembly 36 is removable from thedistal end 34 of arm 32. As depicted, the blade assembly 16 can beconnected to the arm 12 by inserting the projection 70 on the proximalend of holder 6 within orifice 68 in the distal end 14 of arm 12.Likewise blade assembly 36 can be connected to arm 32 by inserting theprojection 90 on the proximal end of holder 8 within the orifice 88 inthe distal end 34 of arm 32.

FIG. 5 depicts the arms 12 and 32 of the arm assembly 4 in an openposition. In this position it can be seen that arms 12 and 32 are joinedone to another by a pair of cross members 72 and 92, which are joinedtogether by a cross member pivot 100. The cross member 72 is connectedto arm 32 via a pivot 98 and to arm 12 via a rod 74, which is moveablealong the length of slot 76. Likewise the cross member 92 is connectedto arm 12 via a pivot 78, and to arm 32 via a rod 94, which is moveablealong the length of slot 96. One skilled in the art will recognize thatthe handle assembly 2 may be removed from the arm assembly 4 by removingthe pins 62 and 82 from their respective holes 64 and 84, resulting inthe device 11 depicted in FIG. 12. This may occur at any time, e.g.prior to or during sterilization of the retractor 10 or during asurgical procedure once the retractor 10 has been opened. Removal of thehandle assembly 2 during surgery may afford a member of the surgicalteam greater freedom of motion, an improved field of view or both.

As can be seen in FIGS. 4 and 5, the blade assemblies 16 and 36 can beremoved from the arm assembly 4. One may find it convenient to removethe blade assemblies 16 and 36 in order to expedite sterilization of theblade assemblies 16 and 36 and/or in order to exchange one or both bladeassemblies 16 and 36 for other blade assemblies (e.g. different sizeblades, different configuration of blades, etc.) as discussed in moredetail herein.

FIG. 6 is an exploded view of the retractor 10 with the blade assemblies16 and 36 in an open position. FIG. 7 is a view of retractor 10 fromabove in a closed position. In this view it can be clearly seen that thebiasing spring 52 tends to bias the handles 12 and 32 apart. Also shownin this view are axes z and z′. In some embodiments, the bladeassemblies 16 and 36 are adapted to rotate about the axes z, z′. In someembodiments, these added degrees of freedom permit the blade assemblies16, 36 to be rotated outward so that they are farther apart at the lowerparts of the blades than at the top. This allows the retractor 10 tocreate an even larger aperture without having to open the retractor 10any farther. FIG. 8 shows a top view of the retractor 10 in an openposition. As shown in FIG. 8 the ratchet 54 locks into position to holdthe retractor 10 in an open position. FIG. 9 shows the retractor 10 fromabove with the blade assemblies 16 and 36 in open positions. FIGS. 10and 11 are expanded views of blade assembly 36 in closed (FIG. 10) andopen (FIG. 11) positions.

FIGS. 13-19 depict the assembly of an embodiment of a blade assembly 36,which comprises blades 40 and 38. Starting with FIG. 13, left openingblade subassembly 242 comprises blade 40, which is connected to innerbarrel 244. The blade 40 comprises a plurality of teeth 254 connected toa bridge 252, which in turn is connected to the inner barrel 244 suchthat rotating the inner barrel 244 about axis y to the left (clockwise)results in the teeth 254 also turning to the left (clockwise). The innerbarrel 244 has a slot 246 cut into the upper portion 245 of the innerbarrel 244. Specifically, the upper portion 245 of the inner barrel 244is that portion of the inner barrel 244 above the highest point at whichthe bridge 252 connects to the inner barrel 244. Not shown in this viewis a corresponding slot on the other side of barrel 244, which isdepicted in FIGS. 29 and 30 as slot 247, as discussed in more detailherein. The inner barrel 244 also has a lumen 248 through the innerbarrel 244 and an engagement groove 250 circumscribing the inner barrel244 above the slot 246.

The right opening blade subassembly 202 comprises blade 38 comprisingteeth 214 connected to a bridge 212, which in turn is attached to theouter barrel 204. The outer barrel 204 also possesses a lip 209, whichis a ledge about the lower portion of the barrel 204. The bridge 212 isconnected to the lip 209 such that rotation of the outer barrel 204 tothe right (counterclockwise) about axis y results in the blade 38 alsoturning to the right (counterclockwise) about the axis y. The outerbarrel 204 has a lumen 208 as well as a pair of slots 206, 207 cut intoupper portion 205 of the barrel 204. For the sake of clarity, the upperportion 205 of the outer barrel 204 is that portion of the outer barrel204 above the lip 209. The relationship of the slots 206, 207, 246 and247 are depicted in FIGS. 29-31.

In FIG. 29 there is depicted a side view of barrel outer barrel 204 andinner barrel 244. For purposes of clarity, the barrels 244 and 204 aredepicted without the additional components of the blade sub-assembliesattached, such as the blades. As can be seen in FIG. 29, slot 206penetrates the upper portion 205 of outer barrel 204. Slot 207, shown indotted lines, also penetrates the upper portion 205 of the outer barrel204, albeit on the opposite side of the outer barrel 204. The outerbarrel 204 also has a lip 209, as mentioned above, which is below theupper portion 205 of the outer barrel 204. Slot 246 penetrates the upperportion 245 of inner barrel 244. Slot 247, shown in dotted lines, alsopenetrates the upper portion 245 of the inner barrel 244, albeit on theopposite side of the inner barrel 244. As shown in FIG. 30, the innerbarrel 244 and the outer barrel 204 have a common axis y, which passesvertically through the lumens (not shown) of the barrels 244 and 204.Axis y thus forms a C2 symmetry axis for slots 206 and 207, as well asfor slots 246 and 247. More specifically, slot 206 forms an angle α withrespect to the y axis, whereas the slot 207 forms an angle −α withrespect to the axis y. Viewed from the vantage offered in FIG. 29, theseangles α and −α have equal magnitude but opposite slope with respect tothe axis y. In a like manner, the slot 246 forms an angle β, withrespect to the axis y and the slot 247 forms an angle −β with respect tothe axis y. Thus slots 206 and 207 possess C2 symmetry about the axis y,as rotation of inner barrel 244 about the axis y results in slots 246and 247 equivalently changing places, as these slots possess congruentangles with respect to the y axis and are located 180° about the axis yfrom one another. Similarly, the slots 246 and 247 possess C2 symmetryabout the axis y, as rotation of the slots 246 and 247 about the yresults in slots 206 and 207 changing places, as these slots areessentially identical with respect to the y axis. Note that α and −βhave similar orientation as do −α and β. This accounts for the oppositerotation of the barrels 204, 244. Note also that in this embodimentangles α, β, −α and −β are essentially congruent, although in someembodiments of the invention it may be desirable for α and −α to differin magnitude from β and −β. One of skill in the art would recognize thatthis latter arrangement would cause barrels 204 and 244 to rotate atdifferent rates in opposite directions. Additionally, in the depictedembodiment it is presumed that the slots 206 and 207 are of equal lengthand start and end at essentially the same height as each other. However,it will be understood that the length of the slots 206 and 207 may beaffected inter alia by the method used to form such features in thebarrel 204 (e.g. machining, molding, etc.) and the assignment of C2symmetry to the slot pair 206, 207 is intended as an illustrativeconvenience. More specifically, it is intended that breaking the strictmathematical C2 symmetry of the slots 206, 207 will not affect theoperation of the invention. Likewise breaking the strict mathematical C2symmetry of the slots 246, 247 will not affect operation of theinvention. Thus, lengthening or shortening one of slots 206 or 207,moving one of the slots 206 or 207 up or down the barrel (along the axisy) or both changing the length and the position of one of the slots 206,207 will not defeat the purpose of the invention. Similarly, lengtheningor shortening one of slots 246 or 247, moving one of the slots 246 or247 up or down the barrel (along the axis y) or both changing the lengthand the position of one of the slots 246, 247 will not defeat thepurpose of the invention. Thus, for the slot pair 206, 207 to satisfythe C2 symmetry requirement for the purposes of the present invention,it is sufficient that a portion of the slots 206, 207 satisfy the C2symmetry requirement. Likewise, it is sufficient for a portion of theslot pair 246, 247 to satisfy the C2 symmetry requirement in order forthe slot pair 246, 247 to satisfy the C2 symmetry requirement for thepurposes of the present invention. However, in the currently preferredembodiment, the slot pair 206, 207 possess strict C2 symmetry, as doesthe slot pair 246, 247, within reasonable tolerances (e.g. about +/−2%).It is also noted that, while the slots 206, 207, 246 and 247 aredepicted as having constant slope with respect to the axis y, it ispossible and well within the skill in the art for the slots to haveserpentine or other curved slopes with respect to the axis y so long asthe C2 symmetry requirement is satisfied through at least a portion ofthe slot pairs 206, 207 and 246, 247. (FIG. 31 shows the angles α, −α, βand −β independent of the barrels in order to provide easiervisualization of their relationships to one another.)

FIG. 13 further depicts threaded plunger 260 having a bottom 266 and atop 268. The plunger 260 has a set of screw threads 265 near the top 268and a hole 262 at a right angle to and passing through the y axis. Alsodepicted is a holder 270 comprising a lumen 272 and a projection 274.Additionally there is depicted an adjustment nut (or adjuster) 280having internal threads 286 and two engagement holes 284. Also depictedare a connector pin 292 and two engagement pins 294.

As seen in FIG. 14, the left turning barrel 244 fits within the lumen208 of the right turning barrel 204. The plunger 260 then fits withinthe lumen 248 of the left turning barrel 244, as depicted in FIG. 15. Inthis configuration, the left turning slot 246 crosses the right turningslot 206 forming a passage 261 through which, as depicted in FIG. 16,the connector pin 292 fits. As depicted in FIG. 16, the blades 38 and 40are in a closed position with the connector pin 292 at the bottom of theslots 24. In this configuration, it is seen that the two blades 38, 40interlace to form a substantially planar blade pair, thus rendering theblade pair especially suitable for insertion within a small incision.One skilled in the art will recognize that moving the blades 38 and 40apart will cause the barrels 244 and 204 to rotate in oppositedirections, thereby causing connector pin 292 to rise along slots 246and 206, thereby causing the plunger 260 to rise along the y axis.Conversely, pulling the plunger 260 up along the y axis would cause theconnector pin 292 to rise along the slots 246 and 206, thereby causingthe barrels 244 and 204 to rotate in opposite directions, thus causingthe blades 40 and 38 to move apart. Conversely, starting with theconnector pin 292 at the top of slots 246 and 206, pressing the plunger260 down will cause the connector pin 292 to move down the slots 246 and206, thereby causing the barrels 244 and 204 to rotate in oppositedirections, thereby causing the blades 38 and 40 to rotate toward oneanother. As can be seen in FIG. 17, the assembly of barrel 244, barrel204 and plunger 260 fits through the lumen 272 of the holder 270 so thatthe threads 264 toward the end 268 of the plunger 260 are visible abovethe lumen 272 of the holder 270 and the lip 209 of the outer barrel 204abuts the holder 270. As can be seen in FIG. 18, the adjustment nut(adjuster) 280 fits over the end 268 of the plunger 260 and is held inplace by pushing the engagement pins 294 through the engagement holes284. One of skill in the art will appreciate that the engagement pins294 thus engage the engagement groove 250 on the barrel 244, therebypermitting the adjustment nut 280 to freely turn about the y axis, butpreventing the adjustment nut 280 from moving up or down along the yaxis. The inner threads 286 of the adjustment nut 280 thus engage theouter threads 264 of the plunger 260. Turning the adjustment nut 280about the y axis in one direction causes the plunger 260 to move upwardalong the y axis, while turning the adjustment nut 280 in the oppositedirection causes the plunger 260 to move downward along the y axis. Asexplained above, movement of the plunger 260 causes movement of theconnector pin 292 up and down the y axis. Movement of the pin 260 in onedirection creates force in one direction on the slots in one barrel andin the opposite direction on the slots in the other barrel. Thus, theadjustment nut 280 can be turned to open an close the blade assembly 36.FIG. 19 shows a fully assembled blade assembly 36 in the closedposition.

The blades used in the blade assemblies may have a variety ofconfigurations. FIG. 20 shows an alternate embodiment of a bladeassembly 300 according to the invention, which comprises a holder 302connected to a projection 308, which is adapted to reversibly insertinto the end of an actuator arm (not shown). The blade assembly 300further comprises an adjuster 304 and a plunger 306. The adjuster 304 isthreaded on the inside, just as the plunger 306 is threaded on its outersurface, so that turning the adjuster causes the plunger 306 to move upand down. The plunger 306 operates through the holder 302 to turn theblades 320, 330 in opposite directions as described in more detail withregard to FIGS. 1-13 above. In particular, the plunger 306 operates toturn inner barrel 322 in the opposite direction to outer barrel 332essentially as described above. Inner barrel 322 is connected to bridge312 from which project teeth 316. Together bridge 312 and teeth 316 formthe blade 320. Outer barrel 332 is connected to bridge 314 from whichproject teeth 318 and fan 334. Together bridge 314, teeth 318 and fan334 form the blade 330.

Another embodiment of a blade assembly 300 is shown in FIG. 21, wherethe blade 320 comprises fan 338; and blade 330 comprises fan 336. As canbe seen in FIGS. 22-28, blades 320, 330 can have a variety of lengths ofbridges 312, 314, teeth 316, 318, etc. (In these figures, the samenumbering is used as in FIGS. 1-13.

In some embodiments, the invention contemplates kits comprising aretractor of the invention. In some embodiments, the kit comprises asingle actuator (e.g. a removable handle and arm assembly as describedherein and depicted in the figures, a scissor-like assembly, etc.) and aplurality of removable and exchangeable blade assemblies. In someembodiments, the kit comprises at least three blade assemblies havingamongst the three blade assemblies at least two distinct bladeconfigurations. In other embodiments, the kit comprises from 3 to 12blade assemblies having amongst the several blade assemblies from 2 to12 distinct blade configurations. In some embodiments, the kit comprisesat least two pairs of identical or substantially similar bladeassemblies. In other embodiments, the kit comprises from 2 to 10,especially about 2 to 5 such pairs of blade assemblies. The bladeconfigurations that are represented in such kits can include comb-likeblades, interlocking comb-like blades (as depicted e.g. in FIGS. 1-12),fan-like blades (as depicted in FIG. 21), combinations of toothed andfan-like blades (as depicted in FIG. 20), etc.

It is noted that in some embodiments the threads 286 and 268 can becanted with respect to the y axis to provide mechanical advantage to theoperator opening and closing the blade assembly 36. In particular, thethreads may be canted so that one full rotation of the nut 280 willresult in the connector pin 292 rising from 1/10 to all the way from itslowest position to its highest position. In some embodiments, the userwill be required to perform from about 1 to about 10 full rotations,especially about 2 to about 8 full rotations, and in particular about 2,3, 4, 5, 6, 7 or 8 full rotations of the nut 280 to cause the connectorpin to traverse the length of the slots 206 and 246, thereby moving theblade assembly 36 from its fully open to its fully closed position orvice versa.

A method according to the invention can be visualized by referring toFIGS. 32-35. In FIG. 32, there is depicted a retractor 10 comprising apair of handles 24, 44 and a pair of blade assemblies 16, 36 asdescribed in more detail herein. An incision I having a length L is madein a suitable tissue, such as the skin overlying or in proximity to thelumbar region of the spine. The blade assemblies 16, 36 are in a closedposition and aligned relatively parallel to one another. In FIG. 33, theblade assemblies 16, 36 have been inserted into the incision I. Pressureon handles 24, 44 causes the retractor 10 to open: i.e. blade assemblies16, 36 move apart from one another in the general directions ofdirectional arrows c, d, respectively. As can be seen in FIG. 34, theincision I is stretched open in the direction of the directional arrowsc and d so that it obtains a length L′ greater than length L of theincision. Turning the adjusters 22, 24 in the direction of the curvedarrows about the axes f and g, respectively results in the opening ofthe blade assemblies 16, 36, causing the incision I to open as can beseen in FIG. 35. As can be seen in FIG. 35, the aperture A is openedhaving a length L′ and a width W′. The aperture A thus provides anaccess area of dimensions L′×W′ for surgical personnel to view theoperating field, to pass instruments, sutures, implants and othersurgical materials through the aperture. Reversal of the steps outlinedin FIGS. 32-35 results in a final incision I having substantially thesame length L and essentially no width, just as the original incision I.By way of comparison, in order for a prior art device having a pair ofblades to crease such an aperture, the incision I would have to have alength L′ and the blades would have to have a width of L′. Thus, thepresent invention permits the use of a much smaller incision to createthe aperture. Thus, the present invention permits less invasive surgicalmethods, quicker and more comfortable recovery from surgery andpotentially cost savings for the medical coverage provider.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1. A retractor comprising: (a) a first blade assembly comprising a firstblade rotatable about a first axis, a second blade rotatable about saidfirst axis and an adjuster in mechanical communication with the firstand second blades and adapted to rotate the first and second bladesrelative to each other about said first axis; (b) a second bladeassembly comprising at least a third blade rotatable about a second axisand optionally a fourth blade rotatable about said second axis and, whensaid fourth blade is present in said second blade assembly, an adjusterin mechanical communication with the third and fourth blades and adaptedto rotate the third and fourth blades relative to each other about saidsecond axis, wherein said second axis is different from said first axis;and (c) a means for moving said first blade assembly relative to saidsecond blade assembly along a third axis that is not parallel to saidfirst and second axes.
 2. The retractor of claim 1, wherein the secondblade assembly comprises a third blade, a fourth blade and an adjusterin mechanical communication with the third and fourth blades and adaptedto rotate the third and fourth blades relative to each other about saidsecond axis.
 3. The retractor of claim 1, wherein the first and secondaxes are substantially coplanar with one another.
 4. The retractor ofclaim 3, wherein the first and second axes are coplanar with oneanother.
 5. The retractor of claim 1, wherein the third axis issubstantially perpendicular to the first axis, the second axis or boththe first and second axes.
 6. The retractor of claim 5, wherein thethird axis is substantially perpendicular to both the first axis and thesecond axis.
 7. The retractor of claim 5, wherein the third axis isperpendicular to the first axis, the second axis or both the first andsecond axes.
 8. The retractor of claim 7, wherein the third axis isperpendicular to both the first and second axes.
 9. The retractor ofclaim 1, further comprising a means for locking said first and secondblade assemblies in at least one predetermined position along saidsecond axis.
 10. The retractor of claim 1, wherein two of said bladesare of substantially different sizes in at least one dimension.
 11. Theretractor of claim 10, wherein said two blades of different sizes formpart of the same blade assembly.
 12. The retractor of claim 10, whereinsaid two blades of different sizes form parts of different bladeassemblies.
 13. The retractor of claim 1, wherein at least one of thefirst, second, third and, when present, forth blades is a comb-shapedblade.
 14. The retractor of claim 1, wherein at least one of the first,second, third and, when present, fourth blades is a substantially flatblade.
 15. The retractor of claim 1, wherein at least one blade assemblyis removable.
 16. The retractor of claim 15, wherein both bladeassemblies are removable.
 17. A method comprising the steps of: (a)providing a retractor comprising: (i) a first blade assembly comprisinga first blade rotatable about a first axis, a second blade rotatableabout said first axis and an adjuster in mechanical communication withthe first and second blades and adapted to rotate the first and secondblades relative to each other about said first axis; (ii) a second bladeassembly comprising at least a third blade rotatable about a second axisand optionally a fourth blade rotatable about said second axis and, whensaid fourth blade is present in said second blade assembly, an adjusterin mechanical communication with the third and fourth blades and adaptedto rotate the third and fourth blades relative to each other about saidsecond axis, wherein said second axis is different from said first axis;and (iii) a means for moving said first blade assembly relative to saidsecond blade assembly along a third axis that is not parallel to saidfirst and second axes; (b) adjusting the first and second blades of thefirst blade assembly to be substantially parallel to each other to forma first closed blade assembly; (c) adjusting the third blade, and whenpresent the fourth blade, of the second blade assembly to besubstantially parallel to the first and second blades of the first bladeassembly; (d) making an incision in a tissue of a body; (e) insertingsaid first blade assembly and said second blade assembly within theincision; (f) moving the first blade assembly away from the second bladeassembly along said third axis and along the length of the incision sothat the incision is stretched to create an opening longer than theincision; and (g) adjusting the first and second blades of the firstblade assembly about said first axis to an open position, and, when saidfourth blade of said second blade assembly is present, adjusting thethird and fourth blades of the second blade assembly substantially aboutsaid second axis to an open position, thereby stretching the incisionout from said third axis and creating an aperture in the tissue that islonger and wider than the incision.
 18. The method of claim 17, whereinthe second blade assembly comprises a third blade, a fourth blade and anadjuster in mechanical communication with the third and fourth bladesand adapted to rotate the third and fourth blades relative to each otherabout said second axis.
 19. The method of claim 17, wherein the firstand second axes are substantially coplanar with one another.
 20. Themethod of claim 17, wherein the first and second axes are coplanar withone another.
 21. The method of claim 17, wherein the third axis issubstantially perpendicular to the first axis, the second axis or boththe first and second axes.
 22. The method of claim 21, wherein the thirdaxis is substantially perpendicular to both the first axis and thesecond axis.
 23. The method of claim 17, wherein the third axis isperpendicular to the first axis, the second axis or both the first andsecond axes.
 24. The method of claim 23, wherein the third axis isperpendicular to both the first and second axes.
 25. The method of claim17, wherein two of said blades are of substantially different sizes inat least one dimension.
 26. The method of claim 17, wherein at least oneof the first, second, third and, when present, fourth blades is acomb-shaped blade.
 27. The method of claim 17, wherein at least one ofthe first, second, third and, when present, fourth blades is asubstantially flat blade.
 28. The method of claim 17, further comprisinglocking said first blade assembly and second blade assembly in aposition apart from each other along said second axis.
 29. The method ofclaim 17, further comprising removing at least a part of said means formoving the first and second blade assemblies toward and away from eachother along the second axis.
 30. The method of claim 17, wherein theincision is made in the lumbar region of the back near the spine. 31.The method of claim 17, wherein the method further comprises placing oneor more pedicle screws in the spine of the body.
 32. The method of claim17, wherein at least one blade assembly is removable.
 33. A kit forperforming an operation, comprising: (a) a retractor comprising: (i) afirst blade assembly comprising a first blade rotatable about a firstaxis, a second blade rotatable about said first axis and an adjuster inmechanical communication with the first and second blades and adapted torotate the first and second blades relative to each other about saidfirst axis; (ii) a second blade assembly comprising at least a thirdblade rotatable about a second axis and optionally a fourth bladerotatable about said second axis and, when said fourth blade is presentin said second blade assembly, an adjuster in mechanical communicationwith the third and fourth blades and adapted to rotate the third andfourth blades relative to each other about said second axis, whereinsaid second axis is different from said first axis; and (iii) a meansfor moving said first blade assembly relative to said second bladeassembly along a third axis that is not parallel to said first andsecond axes; and (b) at least one member of the group consisting ofinstructions for using the retractor to perform a surgical operation,scalpels, suture needles, pedicle screws, suture material, spinalimplant material, spinal fusion rods, biocompatible adhesive and closurestaples.
 34. The kit of claim 33, wherein the second blade assemblycomprises a third blade, a fourth blade and an adjuster in mechanicalcommunication with the third and fourth blades and adapted to rotate thethird and fourth blades relative to each other about said second axis.35. The kit of claim 33, wherein the first and second axes aresubstantially coplanar with one another.
 36. The kit of claim 35,wherein the first and second axes are coplanar with one another.
 37. Thekit of claim 33, wherein the third axis is substantially perpendicularto the first axis, the second axis or both the first and second axes.38. The kit of claim 37, wherein the third axis is substantiallyperpendicular to both the first axis and the second axis.
 39. The kit ofclaim 33, wherein the third axis is perpendicular to the first axis, thesecond axis or both the first and second axes.
 40. The kit of claim 39,wherein the third axis is perpendicular to both the first and secondaxes.
 41. The kit of claim 40, further comprising a means for lockingsaid first and second blade assemblies in at least one predeterminedposition along said second axis.
 42. The kit of claim 41, wherein two ofsaid blades are of substantially different sizes in at least onedimension.
 43. The kit of claim 42, wherein said two blades of differentsizes form part of the same blade assembly.
 44. The kit of claim 42,wherein said two blades of different sizes form parts of different bladeassemblies.
 45. The kit of claim 33, wherein at least one of the first,second, third and, when present, forth blades is a comb-shaped blade.46. The kit of claim 33, wherein at least one of the first, second,third and, when present, fourth blades is a substantially flat blade.47. The kit of claim 33, wherein at least one blade assembly isremovable.
 48. A retractor blade assembly, comprising: (a) a first bladehaving attached thereto a first barrel, the first barrel having a wallcircling an axis and defining a first lumen, a first channel in the wallhaving a first slope with respect to the axis and a second channel inthe wall having a second slope with respect to the axis and having C2symmetry about the axis with respect to the first slope, (b) a secondblade having attached thereto a second barrel, the second barrel havinga wall circling an axis and defining a second lumen, a third channel inthe second wall having a third slope at a third angle with respect tothe axis, and a fourth channel in the second wall having a fourth slopeat a fourth angle with respect to the axis, the slope of the third anglebeing opposite in sign with respect to the axis to that of the firstangle and the fourth channel having C2 symmetry about the axis withrespect to the third channel, wherein the first barrel fits within thesecond lumen of the second barrel such that the first and third channelsintersect to form a first gap and the second an fourth channelsintersect to form a second gap; (c) a cylindrical plunger having anaxis, an outer surface, a first end and a second end, the first endhaving a hole through and at a right angle to the plunger axis, and thesecond end having a screw thread cut into the surface of the plunger,the cylindrical plunger fitting within the first lumen of the firstbarrel such that said hole aligns with the first gap and the second gapand the hole, first gap and second gap forming a passage; (d) a rodfitting through the passage such that movement of the plunger along theaxis causes the first barrel to rotate in a first direction and thesecond barrel to rotate in a second direction opposite the firstdirection; (e) a holder possessing a third lumen, wherein the secondbarrel fits within the third lumen; and (f) a nut having an internalscrew thread and fitting over the end of the plunger; whereby rotationof the nut causes the internal screw thread of the nut to engage theplunger screw thread and causes the plunger to move along its axis,thereby causing the first and second barrels to rotate about the axis inopposite directions.
 49. The blade assembly of claim 48, wherein thethird angle is opposite in sign and congruent with the first angle andthe fourth angle is opposite in sign and congruent with the secondangle.
 50. The blade assembly of claim 48, wherein at least the firstangle has a magnitude with respect to the axis of less than about 75°.51. The blade assembly of claim 48, wherein each angle has a magnitudewith respect to the axis of less than about 75°.
 52. The blade assemblyof claim 48, wherein each angle has a magnitude with respect to the axisof about 20° to about 70°.
 53. The blade assembly of claim 48, whereineach channel has a first end and a second end and the nut and plungerare threaded so that the rod moves from the first end of the channels tothe second end within 1 to 10 full rotations of the nut.
 54. The bladeassembly of claim 48, wherein the holder is adapted to be removablyaffixed to an arm of a retractor.
 55. The blade assembly of claim 48,wherein the holder is irreversibly affixed to an arm of a retractor.